1. Field of the Invention
The present invention relates to a ramp used for a load/unload mechanism in a magnetic disc apparatus such as a hard disc drive (HDD) or the like, and more particularly to a ramp formed as a 2-color molded product made of a resin material forming a ramp main body and a material having a higher rigidity than the resin material.
2. Description of the Conventional Art
In recent years, an HDD is introduced to mobile consumer electronics such as a music player, a digital video camera and the like, in addition to a personal computer, and a shock resistant specification is becoming severe. Under such circumstances, as shown in FIGS. 5A to 5B, there arises a phenomenon that a disc a in an inner portion of a case deflects at a time when the HDD is exposed to a shock, whereby the disc a made of a glass or an aluminum and having a high strength comes into contact with a ramp b formed by a resin (POM, LCP or the like) having a good sliding characteristic, and the ramp b is greatly worn away. In this case, since a scattering of a lot of abrasion powder causes a reading and writing error of a head, it is necessary to apply a countermeasure. Accordingly, in order to reduce the abrasion powder, there is employed a countermeasure of forming disc facing surfaces in inner surfaces of a concave disc insertion portion c in the ramp b by a resin (PEI, PI or the like) d having a high rigidity, that is, forming the ramp b as a 2-color molded product made of a resin having a good sliding characteristic and a resin having a high rigidity, as shown in FIG. 5C. In accordance with this countermeasure, it is possible to form the ramp having a reduced abrasion powder caused by a contact between the disc a and the ramp b, and having a high sliding characteristic.
However, in the case that the HDD is exposed to the shock during the time of reading and writing by a head (at a loading time), there arises a phenomenon that the head lifts up on the basis of the contact between the disc a and the ramp b, and a reading error is caused so as to make a problem. In other words, as shown in FIGS. 6A to 6B, since the disc a is deflected by the shock so as to come into contact with the ramp b, the head e lifts up greatly on the basis of inertia (an arrow f in the figure). Next, as shown in FIG. 6C, the lifted head e comes down onto the disc a, the head e and the disc a comes into contact with each other, and the reading and writing error is caused.
In this case, with regard to the structure of the ramp, there have been conventionally known the structures described in Japanese Unexamined Patent Publication No. 2007-280517, Japanese Unexamined Patent Publication No. 2002-279744, Japanese Unexamined Patent Publication No. 2006-323939, Japanese Unexamined Patent Publication No. 2005-310333, and Japanese Unexamined Patent Publication No. 2002-367314, however, none of them is provided with a step structure at a bottom surface portion of the concave disc insertion portion for reducing rigidity of the ramp.